Conveyors for accumulating articles and thereafter discharging said articles in a controlled fashion are known in the art. For example, U.S. Pat. No. 4,120,393 to Motooka et al. and U.S. Pat. No. 3,934,707 to Bowman both show devices for accumulating articles on a conveyor by blocking or lifting these articles from the conveying surface. The Motooka et al. and Bowman references are said to be particularly useful for relatively soft and flexible articles, such as those packed in plastic or metal foil wrappers or articles with insufficient or weakened bottom areas. U.S. Pat. No. 3,251,451 to Conway et al. also shows the concept of lifting an article from a conveyor to temporarily halt its progress.
U.S. Pat. No. 3,930,573 to Wyman describes a drive chain that can be raised to drive or lowered to cease driving selected pallets disposed along a conveyor to thereby provide accumulating ability.
Accumulating conveyors are also known for selectively activating and deactivating groups of rollers in variously defined zones to provide the accumulating function. See, e.g., U.S. Pat. Nos. 4,042,101 to Krammer et al.; 4,266,659 to Meyer et al.; 4,362,238 to Rivette; 4,453,627 to Wilkins; and 4,534,462 to Hoover et al. For example, U.S. Pat. No. 3,718,248 to Muller shows an accumulation roller conveyor in which the direction of article movement is reversible.